(1) Field of the Invention
This invention relates to improvements in a resin panel in which a skin layer is formed on its surface and an expanded layer having a multiplicity of voids is formed inside it and improvements in a method for manufacturing the resin panel.
(2) Description of the Related Art
Registered Japanese Utility-Model Publication No. 2538513 (hereinafter, referred to as Patent Document 1) discloses a technique of forming a resin panel having hollows inside it by blow molding and thereby saving its weight. In the case of this resin panel, the opposed panel surfaces are deformed to form cylindrical support parts therebetween by pressing a parison from both sides with halves of a mold assembly in blow molding and metal pipes are pressed in the support parts, respectively, to provide rigidity.
In the resin panel disclosed in Patent Document 1, however, the contours of the support parts for supporting the metal pipes pressed in them are exposed as recesses at the external surface of the resin panel, which disfigures the appearance of the resin panel. Further, the metal pipes pressed in the support parts increases the total weight of the resin panel correspondingly, which hinders weight saving. Furthermore, since the panel inside is formed not of an expanded layer having a multiplicity of voids but of hollows, deformations such as warpages occur on the surfaces, which further deteriorates the resin panel appearance.